Pump



Sept. 18, 1934. J. K. DOUGLAS 1,974,134

PUMP

Filed Jan. 24, 1931 4 Sheets-Sheet 1 gwuentoz JAMES K. DDLIGLAS.

Sept. 18, 1934.

J. K. DOUGLAS PUMP 4 Sheets-Sheet 3 Filed Jan. 24, 1931 JAMES K.DOUGLAS.

Sept. 18, 1934.

J. K. DOLIGLAS PUMP Filed Jan. 24, 1931 4 Sheets-Sheet 4 Patented Sept.l, 1 934 umraojs'm rum James K. Douglas, Milwaukee, Wis., assigno'r to vThe Oilgear Company, poration of Wisconsin Application J anuary 24,

4 Claims. (01. ma es) This invention relates to positive displacementpumps which have two relatively rotatable parts arranged one within theother and the coacting surfaces thereof separated by a lubricating film5 which is maintained therein by the working fluid of the pump andsubjected at all times to pump pressure.

Such pumps are frequently employed, to perform work which requires thehighest possible degree of accuracy in the delivery rate of the. pumpduring a widevariation in certain factors which tend to change thedelivery rate, such as variation in the viscosity of the working fluid,due to temperature changes, and variation in the pressure of the workingfluid due to variation in the resistance encountered thereby.

The working fluid is ordinarily a good quality of lubricating oil whichprovides a satisfactory film between the coacting surfaces of therelatively rotatable parts but which varies in vis-, cosity inaccordance with the variation in the temperature thereof.

. The clearance between the coacting surfaces of the relatively rotatingparts is ordinarily sumcient to allow a film of oil in its heaviest ormost viscous state to be formed therein and, as this fllm is subjectedto pump pressure and as the parts rotate relatively to each other whenthe pump is in operation, a small volume of oil leaks from between theseparts and another small volume passes from the discharge side of thepump to the intake side thereof so that the volume of oil delivered toan external circuit is less than the volume of oil which passes throughthe pump.

The total volume of oil which is lost by leakage and by passing from thedischarge side of the pump to the intake side thereof is generallydesig-. nated as the slip of the pump, that is, the slip of a pump isthe difierence between. the volume of oil pumped by the pump and thevolume actually delivered thereby to an external circuit.

At room temperatures and under low pressures, this slip is negligiblerelatively to the volumetric capacity of the pump but it increases inresponse to increases in pressure and temperature, the increasedpressure'forcing the 011 more rapidly from between the relativelyrotating parts and the increase in temperature reducing the viscosity ofthe oil and allowing it to flow more rapidly from between the relativelyrotating parts at any given pressure. a

For the purposeo f illustration, the invention died in a pump which hasits has been shown embo cylinders arranged radially in a cylinder barreljournaled upon a central shaft or pintle, its pis- Milwaukee, Wis., acor:

1931, Serial Nat-10,965

tons reciprocated in the cylinders and the cylinder barrel rotated uponthe pintle by a circular driver which engages the outer ends of the.pistons and has its axis of rotation eccentric to the axis of thepintle, and the working liquid delivered. to and discharged from thecylinders through ports and passageways formed in the pintle. A pump ofthis character is fully illustrated and described in Patent No.1,753,562 issued April 8, 1930 to John P.. Ferris. I The pump disclosedin the above patent has been extensively and successfully used but, whenit is employed to operate the hydraulic feeds of certain machine tools,the variation in slip precludes the possibility of accurately anduniformly maintaining a finely graduated feeding speed.

As'an illustration, a pump of thesize' which is ordinarily employed tooperate machine tool feeds has a slip of about 20 cubic inches perminute at moderate temperatures and pressures, but tem-' peratures andpressuresare often created which cause the slip to increase to 30 cubic,inches per minute. T

A variation in slip of 10 cubic inches is small relatively to thevolumetric capacity of the pump but it often happens that a delivery ofonly 20 cubic inches per minute is required to produce a desired feedingspeed and then a. variation of 10 cubic inches in slip will cause anerror of 50% in the feeding speed. In order to reduce slipand tomaintain the net delivery ofthe pump as constant as possible, theclearance between the pintle and the cylinder barrel has been reducedfar below that ordinarily allowed between relatively rotating parts ofcorresponding diameters, and devices responsive to an increase inpresure have been provided for increasing the stroke of the pump tocompensate for the increase in slip caused by the increase in pressure.

It has been found, however, that it is necessary to compensate forvariations in both presi sure and temperature in order tomaintain. thenet delivery of the pump constant. m0

An object of the invention is to provide a pump having a netdelivery'which remains substantially constant throughout a wide range ofvariation in temperature and pressure. a

Another object is to provide apositive displacement pump which isself-compensated for slip.

The invention-is exemplified by the pump illustrated in the accompanyingdrawingsin which the views are as follows: 4 Fig. 1 is a centralvertical se ction through a m pump in which the invention is embodied,certain parts being shown in full and other parts partly broken away.

Fig. 2 is a schematic drawing illustrating the hydraulic circuit of thepump.

Fig. 3 is a transverse section on of Fig. 1.

Fig. 4 is a transverse section on the line 4-4 of Fig. 1.

the line 33 Fig. 5 is a longitudinal section on'the line 5-5 V of Fig.3. I

The pump chosen for illustration is of the same type as the pump shownin Patent No. 1,753,562 referred to above, and the characteristics whichare common to both pumps have not been illustrated in detail norextensively described herein.

The pump mechanism is arranged within and supported by a casing 1 havinga liquid reservoir 2 in the lower part thereof and its front closed by aplate 3 in which the outer end of a pump shaft 4 is journaled.

The shaft 4 is provided at its outer end with means, such as a pulley 5,for connecting the pump to a prime mover and has its inner end connectedto the driver 6 of a variable displacement pump. The driver 6 isjournaled in an anti-friction bearing 7 which is carried by a bracket 8attached to the front plate 3, thereby rotatably supporting the innerend of the shaft 4.

The bracket 8 has a gear pump chamber 9 formed therein and closed at itsfront by the front plate 3 to enclose a gear pump which has its drivinggear 10 fixed upon the shaft 4 and its driven gear 11 arranged upon astub-shaft 12 carried by the bracket 8. r

The gear pump, which has a larger volumetric capacity than the variabledisplacement pump, has its intake connected to the reservoir 2 by asuction pipe 13 and its outlet connected by a low pressure supply pipe14 to the intake of the variable displacement pump and to a controlvalve 15 which isarranged in the front plate 3. The pressure of theliquid delivered by the gear pump is limited by a relief valve 16through which excess liquid is exhausted, as shown diagrammatically inFig. 2.

The relief valve 16 exhausts into a'chamber 17 which is formed in thebracket 8 and cpmmunicates with the chamber 9 and with the front' 19arranged around its outer periphery .for reciprocating an equal numberof hollow pistons 20 in their cylinders 21 which are formed in acylinder barrel 22 and arranged in radial alinement with the flanges 19,the cylinder barrel 22 being journaled upon a pintle 23 which isarranged eccentric to the axis of the driver 6 when the pump isdelivering liquid.

)Each of the pistons 20 has a push pin 24 secured loosely therein andprovided upon its outer end with a crosshead 25 which bears against anantii'riction bearing 26 arranged between it and a hardened bearingplate 27 carried by the corresponding. flange 19. v

The inner face of each 'crosshead 25 bears I I against the flattenedperiphery of an annular posite each flange 19 with an opening 29 throughwhich a push pin 24 extends.

Each of the cylinders 21 has a port 30 formed in the inner end thereofto register alternately with a segmental intake port 31 and a segmentaldischarge port 32 which are formed diametrically opposite each other inthe pintle 23.

When the driver 6 is rotated, the cylinder barrel 22 is rotated and, ifthe pintle 23 is positioned eccentric to the axis of the driver 6,thepistons 20 upon one side of the pintle 23 are drawn outwardly by theflange 28 andthe pistons 20 upon the other side thereof are forcedinwardly by the flanges 19.

The outwardly moving pistons 20 draw liquid into their cylinders 21through the ports 30 and 31 and the inwardly moving pistons 20- expelliquid from their cylinders 21 through the ports 30 and 32, the volumeof liquid delivered by the pump depending upon the position of thepintle 23 relative to the axis of the driver 6. The pintle 23 is carriedby a rock arm 33 having a sleeve 34 arranged at its upper end andjournaled upon a tubular support 35 which is rigidly secured at itsfront end in the bracket 8 and has a stationary arm 36 secured inposition upon its rear endby a clamping bolt 37.

The lower part of the rock arm 33 is provided with an intake passageway38 and a discharge passageway 39 which communicate with the in- 1 takeport 31 and the discharge port 32, respectively, through two passageways40 and 41 formed axially in the pintle 23.

The passageways 38 and 39 are connected, respectively, through two tubes42 and 43 to an in- 1 take passageway 44 and a discharge passageway 45formed in the upper end of the stationary arm 36.

The intake passageway 44 has the low pressure supply pipe 14 connectedthereto and the 1 discharge passageway 45 is connected by an outlet pipe46 to the control valve 15,. as shown diagrammatically in Fig. 2.

The tubes 42 and 43 have their upper ends rounded and fitted in concaveseats 47, which 1 are formed in the upper end of the stationary arm 36in alinement with the passageways 44 and 45, and their lower endsrounded and fitted in concave seats 48, which are formed in plungers 49fitted in the enlarged upper ends, of the passageways 38 and 39.

The rounded ends of the tubes 42 and 43 are held in firm engagement withthe seats 47 and 48 by the fluid pressure against the inner ends ofplungers 49, and also by helical compression 1 springs 50, one of whichis arranged between the lower end of each plunger 49 and a shoulder 51formed in each of the passageways 38 and 39.

The tubes 42 and 43 thus provide flexible connections for the flow ofliquid between the lower 1 end, of the rock arm 33 and'the upper end ofthe stationary arm 36 and allow the arm. 33 to be rocked upon thesupport 35 without affecting this flow of liquid.

The gear pump draws liquid from the reservoir 2 through the pipe 13 anddelivers it through the pipe 14, the passageway 44, the tube 42, thepassageway 38, the passageway 40 and the intake port 31 to the cylinders21. Liquid is discharged from the cylinders 21 through the outlet port32, the passageway 41, the passageway 39,,-the tube 43, the passageway45 and the pipe 46 to the valve 15,; the pressure created by thevariable displacement pump being limited by a high presthinnest andprovides a very between the cylinder barrel and'the pintle.

'su're relief valve 52 which is connected to the pipe 46 and dischargesinto the reservoir 2.

In the prior pump, the cylinder barrel is ordinarily made of cast ironand; the pintle of steel but, in the present invention, the pintle ismade of a metal, such as brass or bronze, which has a much highercoemcient of expansion than the cast iron of which the cylinder barrelis made. Consequently, an increase in temperature will cause the pintleto have a greater diametral expansion than the cylinder barrel with theresultant reduction in the clearance between the same, and thisreduction in clearance corresponds substantially to the reduction in theviscosity of the oil throughout the range of ordinary operatingtemperatures, for instance, up. to 140 F.

In other words, the pintle expands and reduces the clearance betweenitself and the cylinder barrel in response to increases in temperatureand thereby prevents a substantially greater amount of oil from escapingwhen the pintle and the oil are heated than can escapewhen both are 7cold.

In actual practice, the pintle and the bore of the cylinder barrel aretapered slightly and lapped to a close fit, and then the cylinderbarrelis adjusted upon the pintle to provide the closest possiblerunning fit when the pintle and the cylinder barrel are heated to thehighesttemperature, which may be encountered in service, for instance160 F., atwhich time the oil is thin lubricating film For example, acommon size pump has a 1 diameter bronze pintle and a cast iron cylinderbarrel fitted thereon to provide a clearance of about .0006 inches whenhot. If a considerably larger or smaller pintle is employed, materialsareselected which have the correct relative thermal characteristics.

A reduction in temperature causes an increase inthe clearance betweenthe cylinder barrel and the pintle and a corresponding increase in theviscosity of the oil so that the amount of slip remains substantiallyconstant throughout the entire range of operating temperatures.

As the metals which are otherwise suitable for pint1e=constructionareusually too soft to provide high resistance to the wear thereon, thepintle is preferably provided with a shell or covering 53 'of hardmetal, such aschromi'um; to re sist the wear thereon and thiscovering'is genefally applied by plating the pintle with chromiumandthen grinding and fitting, it to the'cylinder barrel. T

The stroke of the pump may be changed, to obtain accurately graduatedchanges in displacement, by operating a control lever 54 secured uponthe front end of acontrol shaft 55 which is journaled in the front plate3 and has a locking lever 56 threaded thereon for securing it inadjusted positions.

The control shaft 55 extends rearwardly through the tubular; support 35and it is held .1 against axial movement by a collar 5'7 and a gear 58which are secured thereon inengagement, re,- a

. spectively, with the front and rear ends of the support 35. t

The gear-58 meshes with an idler gear 59 which is arranged upon a shaft60 carried .by the rock arm 33, and the gear 59 meshes with a gear 61.journaled upon a shaft 62 which is carried by the 23 at the rear endthereof. 1

pintle the gear 61 is eccentric to the The hub 63 of axis of the shaft62 and has an eccentric head 64 journaled thereon and provided with athreaded laterat bore 65 to receive the threaded end of a thrust pin 66.The head 64 is bifurcated along one side of the bore 65 and providedwith a bolt 6'7 for clamping the thrust pin 66 in adjusted positions.

The head of the thrust pin 66 abuts the inner end of a recess 68 formedin the front end of a plunger 69 which is provided upon its rear endwith a guide pin '70 and arranged forreciprocation in a bore '71 formedin a piston '72 and in the stem '73 thereof.

The piston '72 is fitted in a cylinder '74, which is carried by thelower end or the stationary arm 36 and closed at its inner end by anintegralhead '75 and at its outer end by a cap 76, and the stem '73extends through the head '75 and is fitted there-. v into prevent theescape of liquid from the cylinder '74. Q

.The piston '72 is urged against the head by a helical compressionspring '77 which abuts the inner face of the cap '76 and is arranged inan annular recess '78 formed in the piston '72.

The plunger 69 is urged outwardly againstthe thrust pin 66 by a stack ofBelleville spring washers '79 which are arranged in the bore '11 betweenthe inner end thereof and the plunger 69.

The piston '72 has a bore80 of smaller diameter than the bore '71 andcoaxial therewith to receive a helical compression spring 81 which holdsthe washers '79 against movement relatively to the plunger 69 when thepiston '72 is retracted. A still smaller bore 82 in the outer end of thepiston '72 receives the end of the guide pin '10 which extends throughthe washers '79 and the spring 81.

The-cylinder '74 is connected by a duct 83, which is formed in the arm36, to a pipe 84 which is connected to the control valve 15 as showndiagrammatically in Fig. 2, andthe control valve 15 maybe operated todirect liquid from the gear pump to the cylinder '74 to retract thepiston '72 against the resistance of the spring '77.

Retracticn of, the piston '72 allows the pump to increase its strokeuntil a lug 85 on the rock arm 33 engages a stop bolt 86, as will bedescribed hereinafter. The bolt 86 is threaded into the stationary arm36 and is adjusted to arrest further movement of the arm 33 when fullstroke or a predetermined maximum displacement has been reached.

Aspreviously stated, the gear pump has a larger volumetric capacitythanthe variable displacement pump and delivers liquid to the intake of thevariable displacement pump so that it maintains in'the passageways 40and 44 a pressure determined by the adjustment of the relief valve 16.This liquid acts upon the opposed walls of the passageways 40 and 44 andtends to separate them, thereby tending to swing the rock arm 33 uponthe support 35 and holding the thrust pin 66' in engagement with theplunger 69.

When the variable displacement pump is delivering liquid under pressure,the liquid in the passageways 39 and 45 acts upon the opposed wallsthereof and likewise tends to swing the rock arm 33 upon the support 35and, when the pressure of i the discharge liquid becomes high enough tocause an appreciable increase in the slip of the pump, the force exertedby thedischarge liquid is suillcient to compress the Belleville washersand swing slip. I

As variations in temperature cause variations in the diameter of thepintle with the resultant variations in the clearance between the pintleand the cylinder barrel, so that the slip of the pump is maintainedsubstantially constant at any given temperature, and as the pumpautomatically compensates for variations in slip caused by variations inpressure, the net discharge of the pump remains substantially constantthroughout the entire range of operating pressures and temperatures.

The stroke'of the pump is adjusted manually by loosening the lockinglever 56 and operating the control lever 54 to rotate the gears 58, 59and 61. Rotation of the gear 61 causes its eccentric hub 63 to move thehead 64 and the thrust pin 66 toward or from the piston 72.

The hub 63 is shown in the drawings, and particularly in Fig. 3, withits thick part toward the thrust pin 66 so that the pump is at zerostroke. When the hub 63 is rotated, the distance between the axis of theshaft 62 and the outer end of the thrust pin 66 is shortened and thepressure of the discharge liquid swings the lower end of the arm 33toward the piston 72 and increases the stroke of the pump," and theeccentricity of the hub 63 is ordinarily such that the pump is on fullstroke when the thinnest part of the hub 63 is toward the thrust pin 66.

However, the pump is adapted to operate hydraulic mechanisms at variousspeeds, for instance, to operate the feeding mechanism of a machine toolat both feeding and rapid traverse speeds.

In such a case, the pump is adjusted to deliver a volume of liquidconsiderably below its capacity to operate the mechanism at feedingspeed and the control valve is operated to direct liquid from the gearpump into the cylinder 74 at certain intervals.

When the gear pump liquid enters the cylinder 74, it retracts the piston72 and the pressure of the discharge liquid swings the arm 33 to put thepump on full stroke, thereby instantly increasing the delivery of thepump from a predetermined minimum volume to its full volumetric capacityor to a maximum volume which determined by the adjustment of the stopbolt 86. When the valve 15 is operated to disconnect the cylinder '74from the gear pump, the spring 77 sets the pump back instantly to thepredetermined stroke.

- The invention herein se/Liorth is susceptible of various modificationsand adaptations without departing from the scope thereof as hereafterclaimed.

The invention is hereby claimed as follows:

1. In a pump having driving and" driven members eccentric to each other,the combination of means responsive to the pressure created by said pumpfor increasing the eccentricity of said members to thereby increase pumpdisplacement,

means resisting the action of said pressure responsive means andyieldable under the influence of pressures above a predetermined minimumto enable said pressure responsive means to increase the stroke 01 saidpump an amount sufficient to compensate for the increase in the slip ofsaid pump caused by the increase in said pressure, and hydraulicallyoperated means for retracting said action resisting means to increasethe stroke of said pump to a predetermined maximum.

2. A radial inflow pump, comprising a support, a rock arm carried bysaid support and having intake and discharge passageways, a pintlecarried by said rock arm and having intake and discharge ports andpassageways communicating with the intake and discharge passageways insaid rock arm, a cylinder barrel journaled upon said pintle and havingcylinders arranged radially thereto and provided with ports forregistering with said intake and discharge ports alternately, pistonsfitted in said cylinders, a driver for reciprocating said pistons, meansfor rotating said" driver, a stationary arm carried by said support andhaving intake and discharge passageways, an expansion joint connectingeach passageway in said rock arm to one of the passageways in saidstationary arm and spaced from the axis of said support to enable thepressure created by said pump to tend to rotate said rock arm upon saidsupport and swing its free end toward the free end of said stationaryarm and thereby increase the stroke of said pump, and means carried bythe free end of said stationary arm to resist the movement of said rockarm and yieldable to enable said pump pressure to increase the stroke bfsaid pump after said pressure has increased above a predeterminedminimum to thereby compensate for the increase in the slip of said pumpcaused by said increase in pressure.

3. A radial inflow pump, comprising a support, a rock arm carried bysaid support and having intake and discharge passageways, a pintlecarried by said rock arm and having intake and discharge ports andpassageways communicat ing with the intake and discharge passageways insaid rock arm, a cylinder barrel journaled upon said pintle and havingcylinders arranged radially thereto and provided with ports forregistering with said intake and discharge ports alternately, pistonsfitted in said cylinders, a driver for reciprocating said pistons, meansfor rotating said driver, a stationary arm carried by said support andhaving intake and discharge passageways,-

an expansion joint connecting each passageway in said rock arm to one ofthe passageways in said stationary arm and spaced from the axis of saidsupport to enable the pressure created by said pump to tend to rotatesaid rock arm upon said support and swing its free end toward the freeend of said stationary arm and thereby increase the stroke of said pump,a cylinder carried by the free end of said stationary arm, a pistonarranged in said cylinder, a spring urging said piston against the headof said cylinder, a plunger arranged in said piston, a thrust pincarried by said rock arm and engaging said plunger and spring meansurging said plunger against said thrust pin and adapted to be deflectedby said rock arm in response to a predetermined increase in the pressurecreated by said pump to increase the stroke of said pump and therebycompensate for the increase in the slip of said pump caused by saidincrease in pressure. 4. A radial inflow pump, comprising a support, arock arm carried by said support and having intake and dischargepassageways, a pintle carsaid driver, a stationary arm carried by saidsupcrease the stroke of said pump, means carried by the free end of saidstationary arm to resist the movement of said rock arm and yieldable toenable said pump pressure increase the stroke of said pump aftersaid-pressure has increased above a predetermined minimum and therebycompensate for the increase in the slip of said pump caused by saidincrease in pressure, and hydraulic means for retracting said movementresisting means to enable said pressure to increase the stroke of saidpump to a predetermined maxi- JAMES K. DOUGLAS.

